Recently, Impingement problem of femoral component and polyethylene insert after total knee replacement (TKR) has been brought to light by contact pressure analysis using the knee joint simulator. Therefore, adequate motion analysis is important for estimating the impingement between components and improving postoperative exercise. The purpose of this paper is to analyze the impingement of TKR components during stair climbing activity in vivo. Nine patients (Ten knees) with posterior-stabilized (PS) TKR and Ten patients (Twelve knees) with cruciate-retaining (CR) TKR were examined in stair climbing activity. The 3-D position and orientation of the implant components were determined using image matching technique. Kinetic relation between the femoral component and polyethylene insert and between the intercondylar notch and tibial eminence was calculated, and then their impingement was analyzed. In the CR subjects, the femoral intercondylar notch was considered impinging the tibial eminence in hyperextension of stair claiming activity, but there was no such case. In the PS subjects, impingement of the femoral intercondylar notch and the anterior tibial post were observed in hyperextension of stair claiming activity. In addition, it was observed that femoral cam impinge the posterior tibial post in deep flexion or external rotation. This study helps the surgeon be more aware about impingement between components under some conditions and is useful to improve the design of artificial knee joint.
